This application relates to gratings in optical waveguides such as optical fibers and other light-channeling devices.
Optical waveguides include optical fibers, dielectric slab waveguide formed on a substrate, or other light-channeling devices. Such a waveguide may be used to transport light from one location to another in an optical network, within an integrated optical device, or in other settings. A waveguide may be formed by a dielectric channel that is surrounded by one or more dielectric materials with indices of refraction less than that of the dielectric channel.
For example, a typical fiber may include a fiber core, a cladding layer surrounding the fiber core, and possibly other protection layers outside the cladding layer. The refractive index of the fiber core is higher than that of the fiber cladding. Light rays, when coupled into the fiber core within a maximum angle with respect to the axis of the fiber core, can be totally reflected at the core-cladding interface and thus are spatially confined within the fiber core.